Hemophilia B is an inherited disorder of blood coagulation characterized by a permanent tendency to hemorrhage due to a defect in the blood coagulation mechanism. Hemophilia B is caused by a deficiency in factor IX. Factor IX is a single-chain, 55,000 Da proenzyme that is converted to an active protease (factor IXa) by factor XIa or by the tissue factor VIIa complex. Factor IXa then activates factor X in conjunction with activated factor VIII. Hemophilia B occurs in 1 in 30,000 male births. Since the disease displays X-linked recessive inheritance, females are very rarely affected.
Hemophilic bleeding occurs hours or days after injury, can involve any organ, and, if untreated may continue for days or weeks. This can result in large collections of partially clotted blood putting pressure on adjacent normal tissues and can cause necrosis of muscle, venous congestion, or ischemic damage to nerves.
Hemophilia B is treated by administering to the patient either recombinant or plasma-derived factor IX.
However, there are times when treating such patients with factor IX produces less than satisfactory results, and hemorrhaging continues. Thus, there is a need to develop additional therapies for treating hemophilia B.